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The dependence of the electrochemical behavior of perovskite cathodes on the composition of the electrode, the iron impurity content of the electrolyte, the sintering temperature and the operating temperature was investigated. With La{sub... more
The dependence of the electrochemical behavior of perovskite cathodes on the composition of the electrode, the iron impurity content of the electrolyte, the sintering temperature and the operating temperature was investigated. With La{sub .79}Sr{sub .16}Mn{sub .80}Co{sub .20}O{sub 3} cathodes, the current density of the oxygen exchange reaction is more than one order of magnitude higher than that observed with La{sub .84}Sr{sub .16}MnO{sub 3} cathodes. At typical operating conditions, the apparent activation energy of the oxygen reduction reaction is about 2 eV in the case of the La{sub .84}Sr{sub .16}MnO{sub 3} cathodes, but only about 1 eV if La{sub .79}Sr{sub .16}Mn{sub .80}Co{sub .20}O{sub 3} cathodes are used. Both the apparent activation energies and the apparent pre-exponential factors of the overall electrochemical reaction are strongly influenced by the sintering temperature and the iron impurity content of the electrolyte.
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The application of photoelectrochemistry as a means to study passive films is reviewed. A description of the theoretical background of photoelectrochemical behavior of passive metal electrodes is given that includes photoprocesses in... more
The application of photoelectrochemistry as a means to study passive films is reviewed. A description of the theoretical background of photoelectrochemical behavior of passive metal electrodes is given that includes photoprocesses in crystalline and amorphous passive films, ...
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Forecasting the state of health and remaining useful life of Li-ion batteries is an unsolved challenge that limits technologies such as consumer electronics and electric vehicles. Here, we build an accurate battery forecasting system by... more
Forecasting the state of health and remaining useful life of Li-ion batteries is an unsolved challenge that limits technologies such as consumer electronics and electric vehicles. Here, we build an accurate battery forecasting system by combining electrochemical impedance spectroscopy (EIS)—a real-time, non-invasive and information-rich measurement that is hitherto underused in battery diagnosis—with Gaussian process machine learning. Over 20,000 EIS spectra of commercial Li-ion batteries are collected at different states of health, states of charge and temperatures—the largest dataset to our knowledge of its kind. Our Gaussian process model takes the entire spectrum as input, without further feature engineering, and automatically determines which spectral features predict degradation. Our model accurately predicts the remaining useful life, even without complete knowledge of past operating conditions of the battery. Our results demonstrate the value of EIS signals in battery manage...
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The lithium ion battery (LIB) is a promising energy storage technology for electric vehicles [1]. The most commonly used cathode material in LIBs is LiCoO2. Lithium ion intercalation/de-intercalation into the layer-structured LixCoO2 can... more
The lithium ion battery (LIB) is a promising energy storage technology for electric vehicles [1]. The most commonly used cathode material in LIBs is LiCoO2. Lithium ion intercalation/de-intercalation into the layer-structured LixCoO2 can result in fast capacity fading. Besides, the kinetic rate of lithium ion intercalation/de-intercalation in the lattice structure is slow which causes low power density.[2] Polyoxometalates (POMs) are transition metal oxide molecular clusters with various structures and have been reported as promising cathode active material for energy storage applications. Due to their multiple redox centers they can undergo fast and reversible redox reactions.[3-5] POMs are expected to undergo redox process as a molecular cluster, thus the stability of the POMs is not depended on the recoverability of its long-term crystal structure. The most commonly used POMs in Li ion Molecular-Cluster Batteries (MCBs) are Mo-based POMs which can achieve a capacity of 270 mAh g-...
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Filme von FeOOH‐Abscheidungen auf Au‐Elektroden werden durch Polarisation in einem Fezthaltigen Elektrolyten erzeugt.
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Direct carbon fuel cells (DCFCs) are high temperature fuel cells which offer the possibility to directly convert the chemical energy of carbon materials (e.g. coal, lignite, char, carbonized biomass) into electricity. In addition to using... more
Direct carbon fuel cells (DCFCs) are high temperature fuel cells which offer the possibility to directly convert the chemical energy of carbon materials (e.g. coal, lignite, char, carbonized biomass) into electricity. In addition to using solid carbon fuels, higher overall efficiencies should be possible because the thermodynamic efficiency is close to 100 %. This means higher than those of conventional fuel cell types for gaseous fuels.DCFC technology can employ three different electrolyte types: Molten carbonate electrolyte (liquid salt), molten hydroxide electrolyte (liquid salt) and solid oxide electrolyte (solid ceramic layer). Recently, also combined technologies have been developed.In this chapter, all the concepts are described and their advantages and difficulties are discussed.
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Electrochemical in-situ STM under clean conditions has been applied to monitor the anion adlattice on Pt (111) in sulfuric acid solution at atomic scale resolution. The maxima observed in the STM images are arranged in a centered... more
Electrochemical in-situ STM under clean conditions has been applied to monitor the anion adlattice on Pt (111) in sulfuric acid solution at atomic scale resolution. The maxima observed in the STM images are arranged in a centered [Formula: see text] structure. This ...
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At medium term, electricity could be partially provided by the utilization of carbon in high temperature fuel cells. The thermodynamic efficiency of a direct carbon fuel cell (DCFC) slightly exceeds 100% in a wide temperature range due to... more
At medium term, electricity could be partially provided by the utilization of carbon in high temperature fuel cells. The thermodynamic efficiency of a direct carbon fuel cell (DCFC) slightly exceeds 100% in a wide temperature range due to the positive value of the reaction entropy change. Thus, the thermodynamic efficiency is higher than those of conventional fuel cell types for gaseous fuels. In DCFC technology, three different main electrolyte concepts are used up to now: two types of liquid salt electrolytes (molten carbonate or molten hydroxide) and a solid oxide electrolyte (solid ceramic layer). For instance, it has been reported that power densities up to 210 mW cm-2 can been achieved at 750 ºC in a molten carbonate based cell, resulting to a real practical efficiency of about 60%. Recently, also combined technologies have been developed in which a maximum power density of 500 mW cm-2 is possible. In this paper, the actual state of technology will be discussed for the differe...
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Research Interests: Engineering, Materials Engineering, Materials Science, Chemistry, Technology, and 15 moreElectrochemistry, Kinetics, Medicine, Physical sciences, Passivity, In situ, Dissolution, Metal, CHEMICAL SCIENCES, XANES, Oxide, Electrode, J. Electrochem. Soc, Nanoscience and nanotechnology, and Physical chemistry and chemical physics
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Lithium ion battery usage has grown significantly in recent years. To obtain the best from the li-ion battery technology, it is important to understand both advantages and the limitations from the fundamental point of view. In lithium-ion... more
Lithium ion battery usage has grown significantly in recent years. To obtain the best from the li-ion battery technology, it is important to understand both advantages and the limitations from the fundamental point of view. In lithium-ion batteries, layer structured graphite is the most commonly used anode material and NMC is one of the modern choices of cathode materials for high capacity Li-ion batteries in the electric vehicle applications [1,2,3]. During the first charging process, the electrochemical reduction of electrolyte components gets deposited on the surface of anode resulting solid electrolyte interface (SEI) layer formation [4,5,6]. It is widely accepted that the batteries benefit from a proper SEI formation, as it can improve their lifetime, cycle life, power capability and safety [7]. Morphological structure of SEI layer formed on HOPG and cathode electrolyte interface (CEI) layer formed on NMC plays an important role in lithium-ion battery (LIB), particularly for its cyclability and safety. For the development of high-performance LIB’s, it is crucial to understand the SEI layer formation on anode side [8] and the less studied corresponding layer formed on cathode side termed as CEI, whose composition and role are debated [9]. Microscopic techniques, which include scanning tunneling microscopy (STM) and atomic force microscopy (AFM) are the most powerful tools to measure the electric current and surface topography [10,11]. Within this work, we present in-situ electrochemical atomic force microscopic (EC-AFM) studies of surface reaction and topographic evolution of SEI and CEI layers formed on HOPG and NMC811 substrates. EC-AFM morphological analysis is also complemented with XPS (X-ray Photoemission Spectroscopy) characterisation for elemental composition, which brings a new insight in the comparison of SEI/CEI decomposition products. Acknowledgements: This work is partially supported by Faraday Institution (EP/S003053/1) and North-East Centre of Energy Materials-NECEM (EP/R021503/1) funded by EPSRC. References: [1] H. Sun and K. Zhao, J Physical Chem C, 2017, 121, 6002-6010. [2] S. Bak, E. Hu, Y.Zhou, X.Yu, S.D. Senanayake, S. Cho, K. Kim, K.Y. Chung, X. Q. Yang and K. W. Nam, ACS Applied Materials &Interfaces, 2014, 6, 22594-22601. [3] P. Rozier and J. M. Tarascon, J Electrochem. Soc, 2015, 162, A2490-A2499. [4] L.Seidl, S.Martens, J. Ma, U.Stimming and O.Schneider, Nanoscale,2016, 8, 14004. [5] D.Xin, L.XingRui, Y. Huijuan,W.Dong and W.Lijun, Chem. Methodol,2014,57,178-183. [6] M.Steinhauer, M.Stich, M. Kurniawan, B.K. Seidlhofer, M.Trapp, A. Bund, N.wagner and K.A.Friedrich, ACS Appl.Mater.Interfaces, 2017,9,35794-35801. [7] P.B. Balbuena and Y.Wang, Lithium-ion batteries solid-electrolyte interface, imperial college press,2004. [8] V. A. Agubra, J. W. Fergus, J. Power Sources, 2014, 268, 153−162. [9] L. Yao-min, G.N. Bruno, L. E. Jennifer, A.G. Andrew, J. Anal.Chem,2016,88,7171-7177. [10] C. Shen, M. Buck, Beilstein J. Nanotechnol, 2014, 5, 258−267. [11] C. Shen, I. Cebula, C. Brown, J. L. Zhao, M. Zharnikov, M. Buck, Chem. Sci, 2012, 3, 1858−1865. Figure 1
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This study reports electrochemical phenomena observed during reduction of H 2 O 2 at n- and p-CuInSe 2 (photo)cathodes in alkine medium (pH 9 to 10). After cycling the electrode potential in a given potential rfange, pronouced hysteresis... more
This study reports electrochemical phenomena observed during reduction of H 2 O 2 at n- and p-CuInSe 2 (photo)cathodes in alkine medium (pH 9 to 10). After cycling the electrode potential in a given potential rfange, pronouced hysteresis is observed between the two half-cycles of the voltammetry. At both n- and p-materials, during the positive sweep a pronouced increase of the cathodic current is observed at potentials positive of aoubt - 0.8 V. In the potential region corresponding to the i/U banch with negative slope, the n- and p-type materials show inverted photocurrents
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Novel low temperature fuel cell (FC) cathode catalyst and support systems will be designed and synthesized. The focus will be on highly active catalyst materials for polymer electrolyte membrane fuel cells (PEMFC) for transportation... more
Novel low temperature fuel cell (FC) cathode catalyst and support systems will be designed and synthesized. The focus will be on highly active catalyst materials for polymer electrolyte membrane fuel cells (PEMFC) for transportation applications. These materials will be fully characterized, benchmarked and validated with a multi-scale bottom up approach in order to signi cantly reduce the amount of precious metal catalyst loadings (< 0.15 g/kW) and to vastly improve fuel cell e ciency and durability. Thereby, materials compatible and stable under automotive fuel cell environment and conditions will be investigated in order to reach a FC lifetime of 5000h. These targets are highly relevant to the call topic requesting ambitious, highly novel concepts for next generation European membrane electrode assemblies (MEAs) for transportation applications. Numerical simulations will be used in order to identify which alloy compositions to strive for in the experimental work. These alloys w...
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Electrochemical impedance spectroscopy (EIS) is a powerful tool for the non-destructive diagnosis of lithium ion batteries (LIBs). Thanks to the measurement over a wide frequency range, electrochemical processes of different kinetics are... more
Electrochemical impedance spectroscopy (EIS) is a powerful tool for the non-destructive diagnosis of lithium ion batteries (LIBs). Thanks to the measurement over a wide frequency range, electrochemical processes of different kinetics are reflected in EIS, which contains rich information on battery aging and degradation. Distribution of relaxation times (DRT) method has been increasingly utilised to interpret EIS data. Compared to conventional EIS presentations such as Nyquist plot and Bode plot, DRT isolates the processes with different time constants and gives an explicit showcase of timescales in the battery [1]. Another advantage of DRT is the possibility to separate contributions from cathode and anode without the meticulous work to make three-electrode cells, given that relaxation time peaks can be identified with half cells [2]. The information acquired through DRT can provide insight into battery degradation paths and help improve data-driven methods for battery diagnosis/pre...
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A novel core–shell heterostructure with multi‐walled carbon nanotubes (MWCNTs) as the core and graphene oxide nanoribbons (GONRs) as the shell (MWCNT@GONR) is investigated for the first time as anode material for Na‐ion batteries (NIBs)... more
A novel core–shell heterostructure with multi‐walled carbon nanotubes (MWCNTs) as the core and graphene oxide nanoribbons (GONRs) as the shell (MWCNT@GONR) is investigated for the first time as anode material for Na‐ion batteries (NIBs) in this study. The MWCNT@GONR material with carboxylic acid groups has been synthesized through unzipping of MWCNTs by a microwave‐assisted process. The influence of the amount of carboxylic acid groups on the electrochemistry of MWCNT@GONR is investigated in this work by applying thermal treatment at different temperatures. In this MWCNT@GONR core‐shell structure, the MWCNTs between flat GONR sheets prevent the restacking problem of graphene and enable penetration of the electrolyte. MWCNTs provide high electronic conductivity and direct electron transfer path while GONRs provide high surface area and defect sites (carboxylic acid groups, COOH‐) that can adsorb more Na ions on the surface thereby increasing capacity. MWCNT@GONR provides high capacit...
Research Interests: Materials Science, Graphene, Carbon Nanotube, Nanotechnology, Ion, and 3 moreOxide, Anode, and Electrolyte
Palladium nanoparticles (Pd NPs) were deposited on highly oriented pyrolytic graphite (HOPG) substrates by using a potentiostatic double-pulse technique. The NPs possessed a narrow size distribution and wide dispersion. The particle... more
Palladium nanoparticles (Pd NPs) were deposited on highly oriented pyrolytic graphite (HOPG) substrates by using a potentiostatic double-pulse technique. The NPs possessed a narrow size distribution and wide dispersion. The particle density was in the order of 109 cm−2. The average height of Pd NPs was controlled in a range of 3 to 50 nm by adjusting the duration of growth pulse. The carbon monoxide (CO) stripping at Pd NPs smaller than 14 nm occurred predominantly at a potential above 1.1 V, which is around 0.2 V more positive than that at bulk Pd and larger Pd NPs, due to the small Pd NPs tending to possess well-ordered (111) facets and a high ratio of edge and corner atoms. The high coverage of adsorbed CO (COads) at small Pd NPs can block the formation of adsorbed hydroxyl (OHads) and drive up the oxidation potential. During formic acid oxidation (FAO), small Pd NPs were quickly poisoned by CO, which was formed initially at edges and corner atoms by electrochemical reduction of FAO product CO2 at low potentials. Based on the overall consideration of the low CO tolerance and the high difficulty to remove CO, it must be stated that Pd NPs smaller than 15 nm without strict shape control are not well suited for FAO.
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A FCEV based on bio-ethanol derived from organic waste can be a more sustainable alternative to BEVs and H2-FCEVs.
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ABSTRACT The combination of surface science and electrochemistry is an effective method to approach a fundamental understanding of electrocatalytic systems, especially of the catalyst/support assemblies. Extrinsic chemical defects in the... more
ABSTRACT The combination of surface science and electrochemistry is an effective method to approach a fundamental understanding of electrocatalytic systems, especially of the catalyst/support assemblies. Extrinsic chemical defects in the support can affect the performances and this topic is much investigated in recent electrocatalyst research. In this work, nitrogen functional groups are introduced into the outermost layers of highly oriented pyrolytic graphite (HOPG) by ion implantation with a beam energy of 100 eV. Palladium nanoparticles (Pd NPs) are then electrochemically deposited onto both pure and nitrogen doped HOPG (N-HOPG). Pd2+ species located at the interface between the NPs and the nitrogen-rich surface were observed in the latter case. The supported Pd NPs on N-HOPG show the same electrocatalytic activity for oxygen reduction reaction (ORR) as compared with those supported on pure HOPG. However, the stability of Pd NPs on N-HOPG towards potential cycling decreases strongly due to the existence of Pd2+ at the interface, which can accelerate the dissolution of Pd atoms. This result is contradictory to results on supported Pt NPs from the literature where the merit of the N-doping was outlined.
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ABSTRACT The possibilities of scanning tunnelling microscopy (STM) for the study of metal deposition and dissolution reactions under in situ electrochemical conditions will be described and illustrated by examples. The metal reaction... more
ABSTRACT The possibilities of scanning tunnelling microscopy (STM) for the study of metal deposition and dissolution reactions under in situ electrochemical conditions will be described and illustrated by examples. The metal reaction being studied is copper deposition and dissolution on foreign substrates such as Au(111), or polycrystalline copper. Data on atomically-resolved copper adlayers and on bulk copper deposition on gold will be presented. In addition, time resolved in situ STM for the study of copper deposition and dissolution on polycrystalline copper will be shown as well. From the latter local reaction rates can be estimated. The necessity to consider a possible influence of the tip on the results will be emphasized and the reasons for such an interference of the tip will be briefly discussed.
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Carbon films which are referred to as amorphous hydrogenated carbon (a-C:H) have been investigated using photocurrent spectroscopy. Photocurrent spectra were measured at various potentials in 1M NaClO 4 and 1M NaClO 4 + 0.01M K 4 [Fe (CN)... more
Carbon films which are referred to as amorphous hydrogenated carbon (a-C:H) have been investigated using photocurrent spectroscopy. Photocurrent spectra were measured at various potentials in 1M NaClO 4 and 1M NaClO 4 + 0.01M K 4 [Fe (CN) 6 ]/K 3 [Fe(CN) 6 ]